Apparatus for the manufacture of powder metal helical gears

ABSTRACT

Apparatus for pressing powder metal helical gears and similar articles of manufacture wherein the powder is pressed with a twisting motion of the punches. A cam arrangement is described for a pressing apparatus which rotates the punches during pressing.

Unite States Patent Harrington [4 July 18, 1972 [5 APPARATUS FOR THEMANUFACTURE 2,767,428 10/1956 Pingel ..18/16 R x OF POWDER METALI-IELICAL GEARS 3,118,183 1/1964 Gex et al.. ...18/16.5 X 2,319,4795/1943 Ryder 18/30 LA [72] Inventor: Jerry E. Harrington, Center Line,Mich. 2,445,742 7/1943 Hochw 1 T X Assigneez y l C p Park BIOWH XFORElGN PATENTS 0R APPLICATIONS [22] Wed: March 1970 505,815 12/1954Italy .18/16.5 [21] App]. No.: 18,948

Primary Examiner-J. Howard Fllnt, .lr. Attorney-Talburtt and Baldwin[52] 11.8. C1 ..425/78, 425/356, 425/418 [51] Int. Cl. i 1 ..B30b 3/00,83% 1 1/02 57] ABSTRACT [58] FieldolSearch ..|8/16R,5,7,30LA,20T,

18/19 F Apparatus for presslng powder metal helical gears and s1m|lararticles of manufacture wherein the powder is pressed with a twistingmotion of the punches. A cam arrangement is [56] keierenc'es Citeddescribed for a pressing apparatus which rotates the punches UNITEDSTATES PATENTS during Pressing- 2,561,735 7/1951 Haller ..l8/16.5 I 6Claim, 11 Drawing Figures 1 1 A I I] jfl l /4 II 44 J7 J3 fll? jfl 7 y l2/ .fl A! 4n 4; J i y// Patented July 18, 1972 I 7 3,677,672

2 Sheets-Sh 2 V w E11 BACKGROUND This invention relates specifically tothe pressing of powder metal helical gears. In the conventional pressingof powder metal parts a lower tool punch is fastened rigidly to a lowerram of a press. A die is clamped to a press table. An upper tool punchis clamped rigidly to an upper ram of the press. A center pin or corerod is usually fixed securely to a lower center ram of the press, i.e.,a core rod ram if the pressed article is to include a central bore orthe like.

With such an arrangement any inner or outer configuration on the articleto be formed, such as keys, keyways, gear tooth forms, cam contours orany geometric form, must be on an axis with the vertical motion of thepress rams to allow punch entrance into the die for pressing the powdermetal and to allow ejection of the pressed article from the die.

This conventional arrangement for securing tool members to the pressmembers does not allow for any movement of the tools except verticalmovement. Also, conventional vertical pressing is limited for the mostpart to the forming of parts which are not much thicker than aroundone-fourth inch.

SUNINIARY As a result of an investigation of various techniques forpressing powder metals it has been discovered that the application of atwisting or rotary motion to the powder while pressing it allows thefabrication of larger parts then heretofore possible and providesmoreover, parts of more uniform and higher density. Furthermore, therotary motion shifts the powder about in the die causing the powder tofill it better and settle into the die while also allowing for thefabrication of complex shapes having off-axis inner and outerconfigurations of the type described above.

The invention will be specifically described in connection withapparatus for manufacturing powder metal helical gears although it isnot intended to be limited thereto and finds application elsewhere. Forexample, it is readily applicable to the pressing of plastic powder andmay be used to fabricate a wide variety of off-axis configurations.

It is then an object of this invention to provide apparatus for pressingvarious powders into shapes having otT-axis configurations.

It is a specific object of this invention to provide tool motion whichenables the pressing of steep helical angle tooth forms from powdermetal using the basic vertical motion of conventional compactingpresses. This object is accomplished by rotating or twisting the toolsas they press the powder metal. In the case of helical gears, the toolpunches have helical lands and the die has corresponding helical groovesinto which the punches turn.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a detailed side view of apreferred apparatus according to the invention which is shown partly insection;

FIG. 2 is a fragmentary elevational view of the apparatus showing theupper punch and cam arrangement partly in sectron;

FIG. 3 is a fragmentary elevational view of the apparatus showing thelower cam arrangement partly in section;

FIG. 4 is a bottom plan view of the upper punch;

FIG. 5 is a vertical section through the upper punch;

FIG. 6 is a fragmentary view of the upper punch showing the landpatterns thereof;

FIG. 7 is a top plan view of the lower punch;

FIG. 8 is a vertical section through the lower punch;

FIG. 9 is a fragmentary view of the lower punch showing the land patternthereof;

FIG. 10 is a plan view of the die, and

FIG. 11 is a vertical section through the die showing the groove patterntherein.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention,contemplates in its preferred embodiment the pressing of powder metal ina die by subjecting the powder to a compacting pressure from twosubstantially oppositely disposed punches while simultaneously twistingor rotating the punches. In the case of helical gears it is desirable toprovide male helical punches and a female helical die and to rotate thepunches in opposite directions during pressing as the punches move intothe die from opposite directions.

The invention will be better understood after an explanation withreference to a specific preferred embodiment of an apparatus forpracticing the invention as described in the accompanying drawing.

Referring to the drawing, particularly FIGS. 1, 2 and 3, the novelapparatus shown therein includes upper and lower tool members, generallyindicated at 10 and 12 respectively, disposed on opposite sides of a dietable 14. A die 16 having a powder receiving bore 17 is secured to thedie table by a clamping ring 18 and bolt 20 as shown.

Upper and lower tool members 10 and 12 are respectively fastened to theupper and lower rams 22 and 24 of a conventional vertical press (notshown) by means of fixed pressure plates 26 and 28 as shown. Theseplates are fixed in the sense that they are not free to rotate but areonly capable of reciprocating movement according to the movement of therams of the press. Rotary movement of the tool members with respect toplates 26 and 28 is provided by means of rotary pressure plates 30 and32 which are positioned against pressure plates 26 and 28 respectivelyby clamping means such as clamping rings 36 and 38, which are shownbolted to plates 26 and 28 respectively. The clamping rings arepreferably positioned against the rotary plates in combination with setsof ball bearings 40 as shown. Interposed between the plates are bearingassemblies 34 which may consist of precision taper roller bearings asshown. With this arrangement, the tool members are free to rotate withrespect to the press rams. The pressure plates, including the fixed androtary plates, also transfer the vertical movement of the rams to thepunches.

Securely fastened to rotary plates 30 and 32 respectively are upper andlower tool members 42 and 44 which form, along with upper and lower camfollower means such as rollers 46 and 48, a cam arrangement associatedwith the apparatus punch means for imparting a pre-determined twistingor rotary motion to the upper and lower tool members when they areraised and lowered relative to the die for insertion therein. Of course,the arrangement may consist of a pair of oppositely disposed assembliesas shown or only one assembly or more than two if necessary.

Tool members 42 and 44 each include sets of cam track means or channels,such as grooves 50 and 52 which are better seen in FIGS. 2 and 3respectively. The grooves are precision ground to the identical helixangle required on the part to be pressed and are peripherally disposedaround the members. The grooves and rollers may be of any shape such ascylindrical or tapered as is well known in the: cam art. Furthermore,sliding contact or rolling contact may be used although rolling contactis preferred. Upper and lower tool members 10 and 12 are engaged bysuitable cam follower means, such as rollers 46 and 48, which projectinto grooves 50 and 52 respectively. The rollers project inwardly fromand are rotatably secured to their respective cam follower support meanssuch as column assemblies 54 and 56 which are in turn. secured to dietable 14 as shown. The support means positions the cam follower meansfor engagement with the cam tracks. The columns are preferably in pairsand spaced on the center line of die 16 as shown, left and right, topermit entrance over the die for powder fill. Upper and lower oppositelydisposed support means are preferred.

Upper and lower punch means, such as punches S8 and 60, are secured tothe upper and lower tool members by, for example, bolted clamp rings 62and 64. In the embodiment shown, for the manufacture of helical gears,the punches have several peripheral helical lands 66 as best seen inFIGS. 4 through 6 for upper punch 58 and FIGS. 7 through 9 for lowerpunch 60. These lands have a predetermined warp or helix angle dependingon the specifications desired in the helical gear to be pressed. Die 16is correspondingly helically grooved as indicated at 68 in FIGS. 10 and11 to mate with the lands on punches 58 and 60. The helix angle toothform 68 may be machined into the bore wall of die 16 as can be best seenin those Figures.

Lower tool member 12 further includes a core rod assembly generallyindicated at 70 comprising an elongated core rod 72 which is rotatablymounted by means of caged tapered bearing race assembly includingtapered bearings 74 for free rotation within lower tool member 12 asshown in FIG. 1. Assembly 70 may be covered by neoprene seal 76 or thelike as shown. An additional seal such as O-ring 78 may be included inthe upper portion of lower tool member 12 also if desired. The purposeof the seals is to provide protection against the entrance of fallingpowder metal.

When die 16 is filled with powder metal and lower punch 60 is insertedinto the die as shown in FIG. 1, the upper ram of the press is activatedto lower upper tool member 10 into the die. The lower portion 50a oftracks 50 are straight and the upper portions 50b are curved as shown inFIG. 2 so that as punch 58 is lowered it moves down to the die withoutturning and then rotates during insertion.

Accordingly, the lands or edges of the punches move in a helical path asthe punches rotate and move into and out of the die. The exactconfiguration and length of the cam tracks is of course dependent uponthe particular shape of the tooth pattern or the like desired in thepressed article.

The lower tool member 12 undergoes a similar movement but to less extentas can be seen from the differences in position between the two toolmembers in the drawing. Core rod 72, extending through the axial bore 80of lower punch'60 also extends into axial bore 82 of upper punch 58during pressing to form a center hole in the helical gear.

It is important to note that the die does not direct the punches throughthe twisting or rotary motion. Such an approach has been triedunsuccessfully due to the fact that dies are usually made of materialssuch as tungsten carbide which can absorb extremely high pressures butwhich are brittle and have little or no resistance to shear. It istherefore an important feature of this invention that the camarrangement generate the rotary movement during pressing withoutsubstantial aid or direction from the die.

The exact configuration and length of the grooves 50 and 52, the landpatterns on the punches and the groove patterns in the die must ofcourse be complementary and match the predetermined configuration of thegear to be fabricated.

To eject the pressed gear, upper punch 58 is raised and lower punch 60turns upwardly into the die until the piece is ejected. The pressed gearturns freely in the die to permit its ejection therefrom. The punch isthen returned to its initial position and the apparatus is ready topress another piece. After ejection the gear may be subjected to asintering heat treatment or the like to complete its manufacture.

Although the pressing operation of the apparatus disclosed herein hasbeen described as involving the simultaneous downward movement of theupper punch and upward movement of the lower punch, it is contemplatedthat other modes of operation may be used For example, the lower punchmay be inserted into the die and maintained in a fixed position duringpressing by the upper punch. The lower punch would move only to ejectthe pressed piece.

Any powder material may be pressed in this fashion such as plasticpowders, ferrous and non-ferrous metal powders and the like. Thereversal of certain parts described above is possible. For example, thecam tracks could be formed in the column supports and the followerscould be carried by the upper and lower tool members.

It can be seen that the apparatus according to this invention providespunches adapted to be rotatably inserted into a die by the verticalmotion of the rams of a conventional press. A predetermined rotarymotion is provided by a cam arrangement associated with the punches, thearrangement including cam track means and cam follower means whichimpart the predetemiined rotary motion to the punches during insertioninto the die. The helix angle generated by the punch rotation permitsthe punches to enter the die press the part and eject it.

Having described a preferred embodiment of an apparatus, the inventionis defined by the following claims:

1. A powder pressing apparatus comprising:

at least one tool member adapted for reciprocating motion, the toolmember including peripherally disposed helically configured path camtrack means and coacting cam follower means associated with the camtrack means for imparting controlled rotary motion to the tool memberduring its reciprocation,

cam follower support means positioning the cam follower means inengagement with the cam track means,

vertically movable ram means for reciprocating the tool members,

a powder receiving die member positioned to receive an end of the toolmember,

punch means disposed at the end of the tool member for insertion intothe die when the tool member reciprocates,

the punch means and die including mating lands and grooves which are soshaped relative to the configuration of the cam track means such thatwhen the tool member reciprocates and controllably rotates the punchmeans into and out of the die member the rotation imparted to the punchmeans, by the cam track means and cam follower means alone, twists itinto and out of the die member in mating fashion.

2. The apparatus of claim 1 including:

a rotary pressure plate connected to the tool member and oppositelydisposed thereon with respect to the punch means,

a fixed pressure plate overlaying the rotary pressure plate and adaptedfor contact with the ram of a press for transmitting pressure therefromto the rotary pressure plate and the tool body,

a clamping means positioning the rotary plate against the fixed platebut rotatable with respect thereto, and

a bearing assembly positioned between the rotary plate and fixed platewhereby the rotary plate may rotate freely with respect to the fixedplate.

3. The apparatus of claim 1 including:

a pair of oppositely disposed upper and lower tool members,

the punch means comprises upper and lower punches fixed to the inner endof the upper and lower tool members respectively and disposed towardeach other, and wherein the cam follower support means includesoppositely disposed upper supports for receiving the upper tool membertherebetween and oppositely disposed lower supports for receiving thelower tool member therebetween, the supports being positioned on theupper and lower sides of a die table carrying the die member,

the cam follower means comprises a pair of spaced inwardly projectingbodies carried by the supports in a position of engagement with the camtrack means of the tool members, and

the cam track means on each of the tool members comprises spaced groovesfor accommodating the projecting bodies and imparting rotary movement tothe tool members when they are moved toward and away from each other.

4. The apparatus of claim 3 including:

upper and lower rotary pressure plates connected to the upper and lowerends of the upper and lower tool members respectively,

upper and lower fixed pressure plates overlaying the upper and lowerrotary pressures plates respectively, each being adapted for contactwith the upper and lower rams of a press respectively,

clamping means positioning the rotary pressure plates against the fixedpressure plates, and upper and lower bearing assemblies carried betweenthe upper and lower pressure plates respectively to facilitate rotationof the rotary pressure plates with respect to the fixed pressure plates.

5. Apparatus for pressing helical gears or the like from powdercomprising:

a die table a die having a powder receiving bore extending betweenopposite major surfaces thereof, the bore walls having a grooved femalepattern,

means for holding the die to the table,

upper and lower tool members, each member having a pair of equallyspaced helical cam track grooves peripherally positioned thereon, thegrooves extending over at least a portion of the length thereof,

support members positioning the tool members on opposite upper and lowersides of the die for axial reciprocating movement into the die bore fromopposite directions, vertically movable ram means for reciprocating thetool members,

an upper punch fastened to the lower end of the upper tool member,

a lower punch fastened to the upper end of the lower tool member,

each of said punches having a male pattern complementary to that of thefemale die pattem,.

a pair of oppositely disposed cam followers carried by each of the upperand lower support members, said followers extending inwardly of thesupport members into the cam track grooves whereby upon axialreciprocating movement of the tool members axial rotation is alsoprovided to them and to the punches,

the cam track grooves being so shaped relative to the patterns of thepunches and die such that the rotary motion imparted to the punches, bythe cam track grooves and cam followers alone, twists them into and outof the die in mating fashion.

6. The apparatus of claim 5 including:

upper and lower rotary pressure plates connected to the upper and lowerends of the upper and lower tool members respectively,

upper and lower fixed pressure plates overlaying the upper and lowerrotary pressure plates: respectively, each being adapted for contactwith the upper and lower rams of a press respectively,

clamping means positioning the rotary pressure plates against the fixedpressure plates, and

upper and lower bearing assemblies carried between the upper and lowerpressure plates to facilitate rotation of the rotary pressure plateswith respect to the fixed pressure plates.

1. A powder pressing apparatus comprising: at least one tool memberadapted for reciprocating motion, the tool member including peripherallydisposed helically configured path cam track means and coacting camfollower means associated with the cam track means for impartingcontrolled rotary motion to the tool member during its reciprocation,cam follower support means positioning the cam follower means inengagement with the cam track means, vertically movable ram means forreciprocating the tool members, a powder receiving die member positionedto receive an end of the tool member, punch means disposed at the end ofthe tool member for insertion into the die when the tool memberreciprocates, the punch means and die including mating lands and grooveswhich are so shaped relative to the configuration of the cam track meanssuch that when the tool member reciprocates and controllably rotates thepunch means into and out of the die member the rotation imparted to thepunch means, by the cam track means and cam follower means alone, twistsit into and out of the die member in mating fashion.
 2. The apparatus ofclaim 1 including: a rotary pressure plate connected to the tool memberand oppositely disposed thereon with respect to the punch means, a fixedpressure plate overlaying the rotary pressure plate and adapted forcontact with the ram of a press for transmitting pressure therefrom tothe rotary pressure plate and the tool body, a clamping meanspositioning the rotary plate against the fixed plate but rotatable withrespect thereto, and a bearing assembly positioned between the rotaryplate and fixed plate whereby the rotary plate may rotate freely withrespect to the fixed plate.
 3. The apparatus of claim 1 including: apair of oppositely disposed upper and lower tool members, the punchmeans comprises upper and lower punches fixed to the inner end of theupper and lower tool members respectively and disposed toward eachother, and wherein the cam follower support means includes oppositelydisposed upper supports for receiving the upper tool member therebetweenand oppositely disposed lower supports for receiving the lower toolmember therebetween, the supports being positioned on the upper andlower sides of a die table carrying the die member, the cam followermeans comprises a pair of spaced inwardly projecting bodies carried bythe supports in a position of engagement with the cam track means of thetool members, aNd the cam track means on each of the tool memberscomprises spaced grooves for accommodating the projecting bodies andimparting rotary movement to the tool members when they are moved towardand away from each other.
 4. The apparatus of claim 3 including: upperand lower rotary pressure plates connected to the upper and lower endsof the upper and lower tool members respectively, upper and lower fixedpressure plates overlaying the upper and lower rotary pressures platesrespectively, each being adapted for contact with the upper and lowerrams of a press respectively, clamping means positioning the rotarypressure plates against the fixed pressure plates, and upper and lowerbearing assemblies carried between the upper and lower pressure platesrespectively to facilitate rotation of the rotary pressure plates withrespect to the fixed pressure plates.
 5. Apparatus for pressing helicalgears or the like from powder comprising: a die table a die having apowder receiving bore extending between opposite major surfaces thereof,the bore walls having a grooved female pattern, means for holding thedie to the table, upper and lower tool members, each member having apair of equally spaced helical cam track grooves peripherally positionedthereon, the grooves extending over at least a portion of the lengththereof, support members positioning the tool members on opposite upperand lower sides of the die for axial reciprocating movement into the diebore from opposite directions, vertically movable ram means forreciprocating the tool members, an upper punch fastened to the lower endof the upper tool member, a lower punch fastened to the upper end of thelower tool member, each of said punches having a male patterncomplementary to that of the female die pattern, a pair of oppositelydisposed cam followers carried by each of the upper and lower supportmembers, said followers extending inwardly of the support members intothe cam track grooves whereby upon axial reciprocating movement of thetool members axial rotation is also provided to them and to the punches,the cam track grooves being so shaped relative to the patterns of thepunches and die such that the rotary motion imparted to the punches, bythe cam track grooves and cam followers alone, twists them into and outof the die in mating fashion.
 6. The apparatus of claim 5 including:upper and lower rotary pressure plates connected to the upper and lowerends of the upper and lower tool members respectively, upper and lowerfixed pressure plates overlaying the upper and lower rotary pressureplates respectively, each being adapted for contact with the upper andlower rams of a press respectively, clamping means positioning therotary pressure plates against the fixed pressure plates, and upper andlower bearing assemblies carried between the upper and lower pressureplates to facilitate rotation of the rotary pressure plates with respectto the fixed pressure plates.